DE1911974A1 - Fuel elements for neutronic nuclear reactors - Google Patents

Description

ALEXANDER R. HERZFELD 6 Frankfurt a, m, wis

LAWYER AT THE LAND COURT FRAN KFU RT ON MAY N LAWYER sophienstrasse

Applicant: United States Atomic Energy Commission Washington D. G., USA

Fuel elements for neutronic nuclear reactors

The invention relates to fuel elements for neutronic nuclear reactors, in particular an integral one that can optionally be vented and is composed of individual fuel pins Fuel assembly and a method for its manufacture.

Fuel assemblies with a plurality of fuel pins are known and are widely used in neutronic nuclear reactors in use. The storage of the individual fuel pins in The means used for the fuel assembly must avoid excessive shaking or vibration of the fuel pins and keep the pressure drop of the coolant flow as low as possible. Furthermore, a structure of the fuel assembly that is easy to manufacture from the individual fuel pins and bearing means is intended to be possible.

GIROKONTO 480/6853 DEUTSCHE BANK A. G. FRAN IiFOBr A. M. POSTSCHECK FRANKFURT A. M. 64 36 5

The main disadvantage of the known, from individual fuel pins composite fuel assemblies lies in the difficulty of their manufacture. This is especially the case This is the case when the individual fuel pins are vented to remove the gaseous fission products. The production of such Fuel assemblies require numerous work steps of welding or other mechanical connection.

In the United States application, Serial No. 717} 2-56, the applicant an improved one to simplify manufacture Proposed fuel assembly. However, there are still some manufacturing difficulties here, ζ. B. in terms of Alignment of the pipe sections during the connection, possible embrittlement of the metal cladding or Formation of fine cracks, the elaboration of the deformed wall parts, the closure of the upper pipe ends, in particular when using the opening procedure disclosed in the application.

The invention has an easily manufactured, possibly in a vented arrangement usable fuel assembly of the pen-shaped type to the task, which in particular the Zanl the work steps required for the mechanical connection are greatly reduced, easy alignment of the Firing pins in a row during assembly allows all of them to be vented together at the same time Also arranged burning pens are permitted.

For the production of the fuel assembly according to the invention. essentially cylindrical burning pins in a short, her one. End adjacent but some distance from deformed it located section to a rectangular cross-section. The firing pins are then placed in a Put the smaller faces of the deformed section together and a connecting pin goes through into the overlapping surfaces provided © openings through the entire row of burners inserted. Then the burning pins laugh at the buttocks £. by cold soldering together connected and now form a series of integrally connected Breaaaetifte. Taller legs of fuel pins become side at. Side arranged uad form a fuel assembly. Becomes a If a vented fuel element is sought, the Tferbindungsatift be formed in the fora of an Eolilrohrs, which over Radial 6ffmingeii a flow exchange of the fuel pin enables. At least one fuel in every line of Brenaa pencils will then be arranged for the exhaust gases vented «,

The invention will be explained in more detail with the aid of the drawings. It demonstrate:

FIG. 1 is an isometric view of a detail of a firing pin deformed in accordance with the invention j "'"' ^a ' ^J * ^;> "'"'""' ^Λ '""

Figure 2 in longitudinal section de.n assembly exBei? Hay from. fuel pins shown in Figure 1

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FIG. 3 shows the row of fuel pins from FIG. 2 in cross section along the horizontal cutting line 3-3 »

FIG. 4 shows a single fuel pin in longitudinal section the section line 4-4 of Figure 2;

FIG. 5 shows the isometric view of two according to the invention and connected to a common collecting line by two different methods.

FIG. 1 shows an otherwise known, tubular housing 1 for a cylindrical fuel pin, which has a deformed section 2 adjacent but at a certain distance from its upper end. This has a rectangular cross-section with the side surfaces 3 and 4 of greater or smaller lengths. The side surfaces 3 are limited to a length which is greater than the remaining circular cross-section of the housing 1, so that, according to the order in FIGS. 1, 2 and 3, the deformed attachment 2 protrudes radially over the 3-part with a circular transverse step. The length of the sum of the side surfaces 3 and 4 "remains approximately equal to the circumference of the remaining portion with circular section. The molding or Verfos? STMG forming the rectangular cross section of the deformed portion 2 can take place in a known way. After loading of the Q-ehäuses 1 jrti the Fuel tablets J? Becomes the lower one

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End of the tubes closed by welding on end caps of known design, not shown. The loading with the fuel tablets 5 already shown in the figure for illustration purposes only take place after a number of fuel pins according to the invention according to the following description and an integral one Lattice-shaped fuel assembly is assembled.

Several tubular housings 1 similar to those shown in FIG. 1, but without fuel pellets 5, are arranged in a row in accordance with FIG. 2 with the surfaces 4 lying next to one another. The openings provided in each abutment surface 4 are aligned with the corresponding openings in adjacent housings. The openings can prior to placing the housing in a row or may be provided subsequently to one, the mounting of permitting through them out Verbindungssbifts, precise alignment to facilitate the openings (see figs. 2 _v 3 and 4). The pin 7 can be solid or, if venting of the fuel pins is desired, hollow. In the latter case, the central bore 8 is connected to the interior of each fuel pin via the radial openings 9 (cf. FIGS. 2, 3 and 4). The pin 7 and the openings 6 are designed to fit the pin 7 into the position shown to ensure precise alignment of the fuel pins from the metallurgical connection and to minimize the risk of gaseous fission products escaping from the fuel pins.

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A typical fuel assembly can e.g. B. from 15 yeasts of each 15 burning sticks exist. Each row is formed individually by adding several, e.g. B. 15 fuel pins together be arranged adjacent and the pin 7 through the Row is pushed through. A cap 10 with a flat Base part and an upwardly curved edge part is then to seal the upper end of the fuel pins onto each housing 1 as shown set. Then the caps 10 with the housings 1 and the adjacent surfaces are nifce one another by cold soldering or the like. Metallurgically connected. The verbiiduiigssbif t on the introductory bell in the openings 6 sealed. Then the density of the connecting parts in each fuel line with the help of known ones Leak test procedure checked.

Two different ways of arranging a head piece for connecting several rows of fuel pins to form an integral fuel assembly are for the sake of explanation shown together in FIG. In practice, of course, only one arrangement is achieved in a given fuel assembly to use. The idea of the invention is to simplify the drawing explained here on the basis of only two rows of a limited number of fuel pins.

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According to the bucket configuration, the one at the end of the row is located Firing pin 31 is elongated and provided with a deformed section 12 which is similar to the deformed section 2, but in FIG its length extension is arranged at right angles to this · The second deformed section 12 is with the corresponding second deformed section of an adjacent row of pins in the same, above with regard to the connection of the in a row of burning pins adjoining burning pins described ¥ connected. An inner connecting pin 12 is similar to de «. Pen ? through the second deformed portion and serves, if ventilated operation is desirable, at the same time as one of the gaseous fission products of the Manifold accommodating rows of fuel pins. The cylindrical transition area 14 between the first and the second formed Section of the end pin 11 is hollow and thus facilitates the flow of the gaseous fission products between the individual pens. One of the end pins 11 is in turn via a suitable, not shown, the fission product gases a large number of fuel elements of a neutronic reactor receiving central air duct vented.

A second Atiisgöetaltung is a Ssmaelrohr 15 with spaced apart, and in a Esuästif t X? fitted in every row of fuel pins® »tubular extension pieces 16 provided · The tube 15 is in turn vented, as in the arrangement described above, via a central collecting tube (not shown)»

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Although both of these header assemblies are shown in the drawing are connected to the end pin of each row of fuel pins, other configurations are usable in which, for. B. Others Pins within a row directly with the head piece are connected.

Following the manufacturing steps explained above, fuel tablets are transferred into the tubular housing the lower ends of which are inserted and these are then hermetically sealed with known sealing caps. Around the lower ends Spacer rings 18 are placed on the fuel pins for stabilization.

The structure described leads to an integral one made of fuel pins assembled fuel assembly, which is easy to manufacture and due to the simplicity and accessibility of the welds is also easily injectable. There is also no restriction then vented operation is possible.

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Claims (7)

19119 7 A Pat ent claims 'Ij fuel assembly for nuclear reactors with multiple rows of in the essential cylindrical fuel pins, characterized in that that this in a short section (2) to a cross section with relatively larger and smaller, flat side surfaces (3) 4-) are deformed and each of the forming a series Pins with at least one of the relatively smaller side surfaces rests against at least one adjacent pin and is metallurgically "connected at the imperfections, and a connecting pin (7) in each row across the boss surfaces the adjacent pins "" is guided. 2. Firing pin according to claim 1, characterized in that in each row at least one fuel pin in a second section axially spaced from the first section (12) corresponding to the first. Section is deformed and with this section at least "one side surface of the deform Section "'of at least one fuel pin of an adjacent row rests, and another through the abutting surfaces Verbiridungssbifb (IJ) is led, whereby the Stossf laugh are also metallurgically connected to one another. 3. Bi'fuinsbift according to claim 2 _? characterized in that the harvest and second verCor.-nten sections (2, 12) j in the ro-. ht «ri V / LnkeL. ', ueiniibJ ^ r are arranged» ^ 0 'JiH6' / 0 S 3 \ _BA0 ORIGINAL 4, fuel assembly according to one of claims 1, 2 or 3, characterized characterized in that the "adjacent to the deformed section" End of each focal point with one made of a flat base part and an edge piece that is bent upwards existing cap (10), is closed, wherein the edge piece is metallurgically connected to the fuel pin, 5 »fuel element according to one of claims 1, 2 or 3» thereby characterized in that the connecting pin or the connecting pins (7 »13) is hollow or * are and with radial openings is or are provided that have a flow connection between the fuel pins and the connecting pin or = -sbifben produced or manufactured. 6. Fuel element according to one of the preceding claims, characterized in that the larger side surfaces are shorter than the diameter of the cylindrical pin part » 7. Fuel element according to one of the preceding claims, characterized characterized in that the fuel pin rub over at least a respective end pin of a row of spaced-apart extension pieces (16) of a collecting tube (15) are connected, the extension pieces with the respective Endjtifb are meballurgically connected and with this put in £ fluid connection .. 909848/05 3 * BATH ORIGINAL Le e rs β s t β